In the description of the background of the present invention that follows reference is made to certain structures and methods, however, such references should not necessarily be construed as an admission that these structures and methods qualify as prior art under the applicable statutory provisions. Applicants reserve the right to demonstrate that any of the referenced subject matter does not constitute prior art with regard to the present invention.
In industrial scale, hydrogen peroxide is mainly produced by an anthraquinone process. In this method anthraquinones which are dissolved in an appropriate organic solvent, are used as a reaction media. The organic solvent is usually a mixture of several organic solvents. The solution obtained by dissolving the anthraquinones in the organic solvent is called “a working solution”.
The anthraquinones (AQ) in the working solution are subjected to reduction with hydrogen (hereinafter referred to as “the hydrogenation”) in the presence of a catalyst (reaction 1) to produce corresponding anthrahydroquinones (AHQ). 
Thereafter the anthrahydroquinones are oxidized with air or with an oxygen containing mixture of gases to convert the anthrahydroquinones into the anthraquinones again (reaction 2). In this oxidation step one mole of hydrogen peroxide is formed per one mole of oxidized anthrahydroquinone. 
Hydrogen peroxide produced into the working solution after the above mentioned process steps is usually separated from the working, solution by extraction with water.
The working solution from which hydrogen peroxide has been separated is returned to the reduction step again, thereby forming a cyclic process. This process can produce hydrogen peroxide substantially from hydrogen and air, and hence it is an extremely efficient process.
The alkyl anthrahydroquinones (AHQ) and the alkyl anthraquinones (AQ) are subjected to a number of secondary reactions during the cyclic process. Hydrogenation of the aromatic nuclei of AQ yields alkyl tetrahydroanthrahydroquinones (THAHQ) (see reaction 4).
While this hydrogenation and oxidation procedure is repeated, alkyl tetrahydroanthraquinone epoxides (reaction 3a), alkyl hydroxyanthrones (e.g. oxanthrone, reaction 3b) and the like are produced by side reactions. Alkyl tetrahydroanthraquinone epoxides, alkyl hydroxyanthrones and the like compounds cannot produce hydrogen peroxide, even when repeatedly subjected to the reduction and oxidation. The production of these useless compounds is relatively small per occurrence of the reduction and oxidation. However, while the circulation is repeated, the abovementioned compounds are accumulated in the working solution and cause various troubles. 
Although oxanthrone (see reaction 3b) can be regenerated to active quinone, further hydrogenation leads to anthrone and, subsequently, to dianthrones which cannot be regenerated and thus represent a loss of quinone (reaction 3c). 
If the nuclei of the alkyl anthraquinones are hydrogenated, the alkyl tetrahydroanthrahydroquinones (THAHQ's or “tetra”) are produced (reaction 4). THAHQ's have an ability to produce hydrogen peroxide by the repetition of the reduction and oxidation like the alkyl anthraquinones. 
If “tetra” formation is not suppressed during hydrogenation or “tetra” is not hydrogenated, an equilibrium is reached, in which the hydroquinone charged to the oxidizer consists exclusively of 2-alkyl-5,6,7,8-tetrahydroanthrahydroquinone (THAQ). Such a system is called an “all-tetra” system. Even in the all-tetra system it is essential to maintain a certain equilibrium between AQ's and THAQ's in order to avoid the formation of further by-products.
The oxidation rate of the THAHQ's is lower than the oxidation rate of AHQ's. As indicated by U.S. Pat. No. 3,752,885, when the THAQ's are used as the media for the reduction and oxidation, an extremely large energy is required in the oxidation step, and hence half or more of the total energy required in a circulation process is consumed in the oxidation step.
It is known from the recent literature concerning organic synthesis that the reaction times of organic reactions are remarkably reduced when the energy necessary for the occurrence of the reaction is introduced to the system by using electromagnetic irradiation.
For example, the principles of the use of microwave irradiation in chemistry are described in detail for example in the book “Microwave-Enhanced Chemistry, fundamentals, sample preparation and applications” edited by H. M. Kingston and S. J. Haswell (American Chemical Society 1997). The microwave region in the electromagnetic spectra corresponds to the wavelengths 1-100 cm and the frequencies from 30 GHz to 300 MHZ, respectively. According to an international agreement, the frequencies 6.78 MHZ, 13.56 MHZ, 27.12 MHZ, 40.68 MHZ, 915±25 MHZ, 2450±13 MHZ, 5800±75 MHZ and 22125±125 MHZ of the electromagnetic irradiation are committed to industrial and scientific use. The apparatus generating microwave energy is called a magnetron or a klystron. The commonly used magnetrons operate at 2.45 GHz frequency corresponding a wavelength of 12.2 cm, whereas klystrons operate at 915 MHZ frequency corresponding a wavelength of 32.8 cm.
There is a wide and continuously increasing literature available in the area of using microwave techniques in organic synthesis. An example of a short summary article of this topic was published by Mingos in 1994 (D. Michael P. Mingos; “Microwaves in chemical synthesis” in Chemistry and industry 1. August 1994, pp. 596-599). Loupy et. al. have recently published a review concerning heterogenous catalysis under microwave irradiation (Loupy, A., Petit, A., Hamelin, J., Texier-Boullet, F., Jachault, P., Mathe, D.; “New solvent-free organic synthesis using focused microwave” in Synthesis 1998, pp. 1213-1234). Another representative article of the area is published by Strauss (C. R. Strauss; “A combinatorial approach to the development of Environmentally Benign Organic Chemical Preparations”, an invited review in Aust. J. Chem. 1999, 52, 8-'1-96).
Further, alkyl tetrahydroanthraquinones (THAQ's) are hydrogenated to alkyl octahydroanthrahydroquinones (OHAHQ's or “octa”, reaction 5). 
Although these octahydro hydroquinones (OHAHQ) are oxidized by oxygen to the respective octahydro quinones (OHAQ's) with the formation of hydrogen peroxide, the reaction is too slow to be important in the formation of hydrogen peroxide. Therefore, until now, “octa” has been regarded as a decomposition product that cannot be regenerated to useful quinone.
In order to avoid the accumulation of the unwanted anthraquinone products, OHAQ, THAQ epoxides, anthrones and oxanthrones to the working solution, subsequent regeneration steps are necessary. It is a commonly known technique, described for example in Ullman's Encyclopedia of Industrial Chemistry, vol. A 13, pp. 447-457 (VCH, Weinheim, 1989) to possess a side-stream of a hydrogenated solution containing THAQ epoxides in contact with basic alpha or gamma aluminum oxide at temperatures 50-140° C. In accordance to this, a German patent DE 1,273,499 (in 1964) describes the conversion of the THAQ epoxide to THAQ via the reduction of one mole of THAQ hydroquinone in the presence of basic alumina catalyst (reaction 6). 
In the optimal working solution, even in the “all-tetra” system, it is essential to have both anthraquinones and tetrahydroanthraquinones present in the working solution. Therefore, another commonly used regeneration step in the hydrogen peroxide process is the regeneration of THAQ's to AQ's (reaction 7). This regeneration step, described for example in US statutory invention registration H 1787 (1999), is commonly performed by possessing an oxidized working, solution container, THAQ's in contact with alumina at temperatures 50-100° C. As the net reaction, three moles of THAQ is converted to one mole of AQ and two moles of THAQ hydroquinone. 
Alternative methods for the regeneration of the working solution used in the production of hydrogen peroxide, appear in the old literature. In U.S. Pat. No. 2,901,491 (1959) is described a method for separation of the active anthrahydroquinones from a hydrogenated old working solution by extraction with a metal hydroxide solution. The anthrahydroquinone salts are further oxidized to anthraquinones and added to the new working, solution as purified compounds.
This method is extremely laborous and expensive. Therefore, it has not been taken into industrial use.
For example, in U.S. Pat. No. 3,432,267 there has been reported that the regeneration of the working solution can be accomplished by treating the working solution with ozone, further treating it with an aqueous caustic soda solution, and then passing it through active alumina at 70 to 75° C. However, this regeneration method comprises 3 steps and it is complicated, and since expensive ozone is used problems regarding economy and an apparatus are present.
In U.S. Pat. No. 3,965,251 there has been suggested a method for regenerating the alkyloxyanthrones by treating the working solution at 130° C. in the presence of a catalyst supporting palladium by the use of an olefin. A large amount of the olefin and the expensive platinum group metal are used in this method. Therefore, this method is also considered to be an economically disadvantageous process.
Furthermore, as a method for converting the alkyl tetrahydro-anthraquinones to the alkyl anthraquinones, Japanese Patent application No. 4474/1964 (JP Kokai 39-4474) has reported that the alkyl tetrahydro-anthraquinones can be converted to the alkyl anthraquinones by bringing alumina, magnesia, a spinel of magnesia-alumina or a metal having a hydrogenation ability such as palladium, platinum or nickel into contact with the working solution and a compound having an unsaturated bond, such as an olefin. Also in this case, however, in order to heighten a reaction rate, a large amount of the olefin is used and the employment of the expensive platinum group metal is required. Hence, the reported method is also considered to be an economically disadvantageous process.
When the regeneration steps are performed by treating the working, solution by aluminum oxide, remarkable amounts of aluminum oxide are needed. Furthermore, the aluminum oxide is deactivated by water formed in the regeneration step. The aluminum oxide is also gradually covered by polymeric aromatic by-products resulted from the polymerization of the aromatic compounds of the aromatic solvent, nowadays most commonly used in the working solution. Therefore, the aluminum oxide used for the regeneration steps must be changed occasionally. The regenerating of the working solution is a costly and sometimes a limiting step of the process. Any improvement in increasing the effectivity of the regeneration steps or the life time of the aluminum oxide will result in substantial savings in the cost of the production of hydrogen peroxide.
Since the used aluminum oxide is contaminated by anthraquinone derivatives and by the phenolic derivatives, the purification of the used aluminum oxide discharged from the hydrogen peroxide process is extensively studied by the applicants. However, the purification of the used aluminum oxide has been found too expensive to carry out. Being a relatively non-toxic material, it is commonly stored to the landfill areas. However, the storage of the used aluminum oxide to the landfill areas possesses an environmental problem at least by occupying a remarkable space in the landfill area. Therefore, also from an environmental point if view, it is extremely desirable to reduce the consumption of aluminum oxide in the production of hydrogen peroxide.